The objective of these studies is to assess the sensitivity of the human pituitary gland to hypothalamic gonadotropin releasing hormone (GnRH), and to quantitate circulating GnRH in various physiologic and pathologic states. The following facets of the hypothalamic-pituitary system are being assessed: 1) the modulating effects of varying concentrations of gonadal steroids on the capacity of the pituitary to respond to GnRH; 2) possible changes in pituitary responsiveness to GnRH at various times postpartum; 3) differences in response to synthetic GnRH and other substances which affect hypothalamic function in normal subjects and patients with suspected benign or malignant hypothalamic pituitary disease.